1. Field of the Invention:
The present invention relates to communication systems and more particularly to a communication receiver capable of operation in a global satellite communication system.
2. Description of the Prior Art
Several communication systems have been described for providing nationwide communication coverage. One such system is a nationwide paging system described in U.S. Pat. No. 4,644,347 to Lucas, et al., entitled "Multiple Frequency Message System" which is assigned to the assignee of the present invention. In the nationwide paging system of Lucas, each geographical area covered by the system includes one or more local service providers operating on one or more paging channels, and a nationwide service provider operating on a nationwide paging channel. Synthesized paging receivers are provided in the system which are capable of operating on a home, or local channel, when the paging receiver is operating in the home geographic area to which the receiver is assigned. In other geographic areas outside the home geographic area which are covered by a nationwide service provider, the paging receiver operates on the nationwide paging channel. The frequency of operation of the receiver is automatically controlled by means of a special transmitted coded signal which is uniquely assigned to both the local paging channels and the nationwide paging channel in each geographic area. In normal operation, when the paging receiver detects the assigned special coded signals on either the local or the nationwide paging channel, the paging receiver reverts to the local paging channel for reception of the transmitted pages. When the paging receiver is outside of the local geographic area, failure to receive the assigned special coded signals, results in the paging receiver to begin searching for a nationwide channel, eventually reverting to the nationwide paging channel, when one of the assigned nationwide paging channels is detected. While such a system as described provides complete "hands off" operation of the paging receiver with regards to channel selection in those geographic areas where a service provider is operating, there may be significant time intervals while the paging receiver is in transit from one location to another, wherein messages directed to the paging receiver must be stored for transmission at a latter time, or where the message are lost due to transmission of the messages when the paging receiver is not within a geographic area where a service provider is operating.
Several proposed nationwide paging systems have addressed the issues of transmission of the messages from one geographic area to another when the user is in transit. One such system is described in U.S. Pat. No. 4,178,476 to Frost. Frost stores the messages while the user is in transit between those geographic areas providing nationwide paging coverage, as do other of the nationwide paging systems.
As described, the currently available nationwide paging systems provide only limited nationwide paging coverage. The coverage is limited because the present nationwide systems provide operation only in those metropolitan areas where a paging system infrastructure is in place. This results in the requirement for the storing and later transmission of pages as described, as the metropolitan areas seldom adjoin sufficiently to provide continuous paging coverage. A nationwide paging system is needed which can not only provide nationwide paging services to those service areas having a paging system infrastructure, but also to those geographic areas which do not presently have a paging system infrastructure.